Algae formation, switch to liquid chlorine 10% bleach

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Kuppuswamy

0
Sep 21, 2016
7
Round Rock, Texas
I am new to this site. Since last 6 months I have been operating my pool by using Trichlor 3" tablets for FAC and Calcium Hypochlorite 56% for shock. Since supply water is good, parameters like TA (80 ppm), Calcium Hardness (260 ppm), pH (7.6) etc. have been good, needing no chemical addition. Main control issues were FAC (maintained by frequent shock doses), Algae formation and rise in DE filter pressure from 25 psi start to 35 psi (max) in 3 months.

Recently FAC became nil and on analysis CYA was 100 ppm (checked at vendor shop). Replaced around 5500 gal of water out of total 17500 gal (though recommended to be double that but limited by disposal issues) and switched from Trichlor to 10% liquid chlorine bleach (added 2 gal few days back and another half gal today) to limit algae and filter pressure rise. This has helped only to a limited extent. Filter pressure has also risen to 35 psi in less than a month and needs an immediate back-wash.

What is the way forward. Usage of pool is limited to two of us. Not rechecked CYA again, but will replacing another 6000 gal or so help? Can 10% bleach be used both for control and shock. Should I then discontinue Trichlor tabs? Any other additives?

Appreciate any suggestions on the above.

Thanks

Kuppuswamy
 
Kuppuswamy said:
I am new to this site. Since last 6 months I have been operating my pool by using Trichlor 3" tablets for FAC and Calcium Hypochlorite 56% for shock. Since supply water is good, parameters like TA (80 ppm), Calcium Hardness (260 ppm), pH (7.6) etc. have been good, needing no chemical addition. Main control issues were FAC (maintained by frequent shock doses), Algae formation and rise in DE filter pressure from 25 psi start to 35 psi (max) in 3 months.

Recently FAC became nil and on analysis CYA was 100 ppm (checked at vendor shop). Replaced around 5500 gal of water out of total 17500 gal (though recommended to be double that but limited by disposal issues) and switched from Trichlor to 10% liquid chlorine bleach (added 2 gal few days back and another half gal today) to limit algae and filter pressure rise. This has helped only to a limited extent. Filter pressure has also risen to 35 psi in less than a month and needs an immediate back-wash.

What is the way forward. Usage of pool is limited to two of us. Not rechecked CYA again, but will replacing another 6000 gal or so help? Can 10% bleach be used both for control and shock. Should I then discontinue Trichlor tabs? Any other additives?

Appreciate any suggestions on the above.

Thanks

Kuppuswamy
Click to expand...
My first suggestion is to stop going to the pool store. Their only response it to sell you something.

I will tell you, it didn't turn like it is overnight and it will take time to clear. But, we can teach you how to get it sparkling and keep it that was for a lot less money than the pool store.

Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. But, what can you do?? We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit. Order a TF100 and at least include the XL option. That will give you what you need while you are clearing the pool, and probably enough reagents for a couple of years normal use. Once you get your test kit and we can see some numbers we can trust we can provide more suggestions for water care. Right now any suggestions would just be a guess.

While you wait for it to get delivered, you have a homework reading assignment. Start with ABCs of Water Chemistry and Turning Your Green Swamp Back into a Sparkling Oasis

The filter pressure is rising because it is doing it's job, filtering out junk in the water, which at this point is probably lots of living and dead algae. You are killing some of it, but not all.
 
Thanks. Ordered TF 100 test kit with stirrer and XL option. Meanwhile as the filter pressure was too high at 35 psi, carried out back wash. Restart pressure normal at 25 psi, flow is increased quite a bit looking at the turbulence and water has cleared with greenish sediments settled down at pool bottom. Polaris is on its cleaning job.

Meanwhile, expect to revert with water analysis hopefully by Wednesday.
 
Got the TF 100 Test Kit and the Magnetic Stirrer (MS) today and went ahead with the testing. The MS lights comes on but goes off on releasing the power button and stirring does not take place. Disappointed, will check later. Any suggestions? I mixed manually but looks like it is beneficial for CH and TA tests only (not used for FC/CC due to staining of cylinder). If the thing doesn't work will have to return.

Test results are OTO 2-4; FC 2.5; CC 2.0 (hence TC 4.5); CYA 90; pH 8.2; TA 120; CH 525. pH and TA rise seem from high liquid chlorine addition (one more gallon 10% LC added in three installments to keep chlorine level), but no acid. The solution from pool math shows draining to the extent of 50-55% will get CYA down to 40 (when CC will also come down) and CH down to 260 (when CSI wii reduce from 0.88 down to 0.06). Can't explain CH level doubling compared to vendor results.

Algae cleaned manually, pool looks nice. Look forward to your expert advice. With temperature dropping wonder how much use time I can get.
 
Magnetic Stirrer fixed now running ok. So only need the suggested way forward and also to keep it running in the cold season. Minimum temperature here is typically 30 F and I have a 30" wall on one side of the pool that will restrict putting up a pool cover with water bags.
 
Just checked make-up water (garden supply) CH, found it to be 150 ppm (Household use has a softener with CH <25). Reworked PoolMath, shows 60% replacement to get CH down from 525 to 300 and CYA from 90 to 35. CSI will come down from 0.88 to -0.29.

Appreciate your suggestions asap.
 
Replaced only 4600 gal pool water (as pump lost suction, earlier was ~4000 gal and not 5500 gal). Added 61oz 31.5% HCl circulated and tested. Got pH down to 7.3 and CYA 60. Other results were TA 110, CH 275 (using Mag. Stirrer), CSI -0.13. Calculated 4gal 1qt of 10% Bleach for FC of 24, but got a FC of 27 with just 3 gal. Before that scrubbed the pool for removing all algae. FC held for 13 hours (other results are pH 7.8, CC 1.5, TA 110 and CSI 0.35) as of 4th Oct. 8am. The pool was absolutely clear and no algae. The day was sunny with temperature rising to 88 F.
Added another 17 oz of HCl yesterday evening to get the pH down to 7.5. Today noon test showed pH 7.5, FC 17.5, CC 0.5 and assuming no change in TA, CH and CYA, CSI is 0.06. Small patches of algae was forming on the wall and cleaned to the extent possible (cannot enter the pool). Don't want to drain any more and plan to keep FC of 7-9. Please advice what else to be done to prevent algae formation. Is FC loss excessive for a day?
 

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